Curing compound and method of curing halogenated polymers

ABSTRACT

Additives including dithiocarbamyl derivatives of 2,5-dimercapto-1,3,4-thiadiazole (DMTD) useful as curing agents and accelerators. Curable polymer compositions including at least one halogenated polymer and at least one additive including the dithiocarbamyl DMTD derivatives. A method is also disclosed for preparing a cured polymer by admixing at least one halogenated polymer with at least one additive including the dithiocarbamyl DMTD derivatives and subsequently curing the composition.

BACKGROUND OF INVENTION

[0001] The present invention relates to thiadiazole derivatives usefulas accelerators and/or curing agents for halogenated polymers in rubbervulcanization processes, and to halogenated polymer compositionscontaining the thiadiazole derivatives, as well as a method of preparingthe same.

[0002] Vulcanizable rubber compositions present certain inherentproblems in terms of handling and storage. For example, prior to thecuring, the uncured rubber may often degrade during storage due tohydrolytic instability of the additives contained therein. As a resultthe cure reproducibility from batch to batch in the vulcanizationprocess can often vary. However, batch-to-batch cure reproducibility isan important parameter of quality control.

[0003] It is known that halogen-containing polymers may be compoundedwith curing agents, accelerators and other compounds in order to preparevulcanizable rubber compositions which are useful in a variety ofapplications. A description of curing agents and accelerators, as wellas other components of natural and synthetic rubbers can be found inKirk-Othmer's Encyclopedia of Chemical Technology, John Wiley & Sons,4th Edition, at pages 460-481.

[0004] Despite the availability of curing agents and/or accelerators forhalogenated polymers, there is a continuing need for curing agentsand/or accelerators that allow for good bin storage characteristics andimproved batch-to-batch cure reproducibility.

[0005] Accordingly, it is an object of the present invention tocompounds useful as curing agents and/or accelerators for rubbervulcanization processes which provide good bin storage properties foruncured rubber and improved consistency in cure reproducibility.

[0006] It is yet another object of the present invention to providecurable rubber compositions which exhibit good bin storage propertiesand improved consistency in cure reproducibility and methods ofpreparing the cured rubber compositions.

SUMMARY OF THE INVENTION

[0007] In accordance with the present invention, an additive is providedincluding a dithiocarbamyl-1,3,4,-thiadiazole derivative having formula(I), or an isomer thereof:

[0008] where R₁ and R₂ are independently a radical being either analkyl, a cycloalkyl, an alkenyl, an aryl, an arylalkyl, or an alkylaryl,or R₁ and R₂ together form a 3- to 7-membered cyclic ring structure; andX is (i) hydrogen, (ii) a dithiocarbamyl radical having formula (II):

[0009] where R₃ and R₄ are independently a radical being either analkyl, a cycloalkyl, an alkenyl, an aryl, an arylalkyl, or an alkylaryl,or R₃ and R₄ together form 3- to 7-membered cyclic ring structure, or(iii) a mixture thereof. In a preferred embodiment, X is hydrogen, andR₁ and R₂ are independently a radical being either an ethyl, anisopropyl, a butyl, or an isobutyl, or R₁ and R₂ together form a6-membered cyclic ring structure, with a piperidyl radical beingpreferred.

[0010] In another embodiment the present invention provides an additiveincluding a dithiocarbamyl-bis-1,3,4,-thiadiazole derivative havingformula (III), or an isomer thereof:

[0011] where X is hydrogen or a dithiocarbamyl radical having formula(II)

[0012] where R₃ and R₄ are independently a radical being either analkyl, a cycloalkyl, an alkenyl, an aryl, an arylalkyl, or an alkylaryl,or R₃ and R₄ together form 3- to 7-membered cyclic ring structure. In apreferred embodiment, X is hydrogen.

[0013] The present invention also provides a curable polymer compositionincluding at least one halogenated polymer and at least one of theabove-described additives of the present invention. A method is alsoprovided for preparing a cured polymer composition including at leastone halogenated polymer and at least one of the additives of theinvention.

[0014] The additives of the present invention are particularly useful ascuring agents and/or accelerators for halogen-containing polymercompositions, and provide good bin storage characteristics for theuncured polymer composition and improved cure reproducibility. These andother advantages of the present invention will be more readily apparentfrom the detailed description set forth below.

DETAILED DESCRIPTION OF THE INVENTION

[0015] It has now been discovered that certain hydrocarbyldithiocarbamyl-1,3,4-thiadiazole derivatives having a disulfide linkageare useful as curing agents and accelerators in halogen-containingpolymer compositions. The thiadiazole derivatives of the presentinvention have been found to provide good bin storage characteristicsand improved cure reproducibility when used as additives inhalogen-containing polymer compositions.

[0016] In one embodiment an additive is provided that includes adithiocarbamyl-1,3,4,-thiadiazole derivative having formula (I):

[0017] where R₁ and R₂ are independently a radical being either analkyl, a cycloalkyl, an alkenyl, an aryl, an arylalkyl, or an alkylaryl,or R₁ and R₂ together form a 3- to 7-membered cyclic ring structure; andX is (i) hydrogen, (ii) a dithiocarbamyl (i.e., DTC) radical havingformula (II):

[0018] where R₃ and R₄ are independently a radical being either analkyl, a cycloalkyl, an alkenyl, an aryl, an arylalkyl, or an alkylaryl,or R₃ and R₄ together form substituted or unsubstituted 3- to 7-memberedcyclic ring structure, or (iii) a mixture thereof. Preferably, X ishydrogen while R₁ and R₂ are independently a C₁ to C₅ alkyl radical suchas an ethyl, an isopropyl, a butyl, or an isobutyl, or R₁ and R₂together form a substituted or unsubstituted 6-membered cyclic ringstructure (e.g., a piperidyl radical).

[0019] In another embodiment the present invention provides an additivethat includes a dithiocarbamyl-bis-1,3,4,-thiadiazole derivative havingformula (III):

[0020] where X is (i) hydrogen, (ii) a dithiocarbamyl radical havingformula (II):

[0021] where R₃ and R₄ are independently a radical being either analkyl, a cycloalkyl, an alkenyl, an aryl, an arylalkyl, or an alkylaryl,or R₃ and R₄ together form 3- to 7-membered cyclic ring structure, or(iii) a mixture thereof. In a preferred embodiment, X is hydrogen.

[0022] The derivatives of formulas (I) and (III) are synthesizedfollowing techniques known in the art. For example, compounds havingformula (I) can be synthesized by reacting2,5-dimercapto-1,3,4,-thiadiazole (i.e., DMTD) with a dithiocarbamicacid in which the amine moiety is a tertiary amine having substituentsR₁ and R₂, or R₃ and R₄. The reaction is carried out in the presence ofan oxidizing agent (e.g., hydrogen peroxide). As known in the art,dithiocarbamic acid is not readily isolatable and thus needs to beformed in situ to provide the starting material. The dithiocarbamic acidintermediate is synthesized in situ by reacting carbon disulfide withthe appropriate secondary amine (e.g., dibutyl amine to form dibutyldithiocarbamic acid). Likewise, compounds of formula (III) where X ishydrogen can be synthesized by first forming in situ bis-(1,4-piperazinedithiocarbamic acid) from homopiperazine and carbon disulfide. Thedithiocarbamic acid intermediate is then reacted with2,5-dimercapto-1,3,4-thiadiazole in the presence of an oxidizing agent.The reaction conditions (e.g., temperature and time) are variable andcan be easily modified by one of ordinary skill in the art following theteachings set forth herein.

[0023] While not wishing to be limited by theory, those skilled in theart will recognize that the additives of the invention may additionallycontain positional isomers of the derivatives having formulas (I) and(III) due to tautomerization or other similar rearrangement of thesubstituents on the DMTD moiety. In accordance with the invention,reference to “an isomer thereof” means positional isomers. Positionalisomers of formulas (I) and (III) are also useful as curing agents andaccelerators. Positional isomers of formula (I) would have the followingstructures:

[0024] Likewise, similar rearrangements for compounds having formula(III) are also expected.

[0025] The above-described additives of the invention, alone or incombination, are admixed with a major amount of at least one halogenatedpolymer to provide a curable (i.e., vulcanizable) polymer composition.The polymer composition is then cured following conventional techniquesknown in the art to produce a cured (i.e., vulcanized) polymercomposition.

[0026] In accordance with the present invention, any saturated orunsaturated halogen-containing (i.e., halogenated) polymer may be used.Preferably, the polymer contains at least one percent by weight halogenwith about five percent being more preferred. The halogen content in thepolymer may range up to 40 percent based on the weight of the polymer.Preferably, the halogen-containing polymers is an elastomer. In anotherpreferred embodiment, the halogen-containing polymer is achlorine-containing (i.e., chlorinated) polymer. Representative examplesof chlorine-containing polymers to be used in accordance with thepresent invention include, but are not limited to, homopolymers ofepichlorohydrin, copolymers of epichlorohydrin and ethylene oxide orpropylene oxide, polychloroprene, chlorinated polyolefins,chlorosulfonated polyolefin, polychloroalkylacrylates and chlorobutylrubber. These polymers are well known in the art and are availablecommercially from variety of sources. One particularly preferredchlorinated polymer is chlorinated polyethylene “CPE” which iscommercially available from DuPont Dow under the tradename Tyrin®.

[0027] The halogen-containing polymers may be blended with non-halogencontaining polymers as along as a sufficient halogen content is providedin the polymer composition to effect crosslinking. The blends caninclude, but are not limited to, natural ruber, polybutadiene,polyolefins, copolymers of butadiene with styrene (SBR) or acrylonitrile(NBR), copolymers of ethylene-propylene-diene (EPDM), butyl rubber andthe like. Such blends may contain from about 10 to about 90% by weightof each type of polymer. In a more preferred embodiment, the blendscontain the halogenated polymer at levels from about 25 to 75% by weightwith respect to the total weight of the polymer blend.

[0028] The additives of the invention may be incorporated into thepolymer composition in their pure form or they may be mixed with one ormore liquid diluents. They also may be adsorbed onto the surface of afinely divided, inert carrier to provide a powdered product. When theadditives of the invention are mixed with a liquid diluent or finelydivided carrier, the additive may range from 15 to 85 percent by weightof the composition with the remainder being the diluent, carrier or acombination thereof. Preferably, the additives of the invention aremixed in a ratio ranging from 30 to 70 percent by weight.

[0029] The suitable diluents, among others, include aromatic, naphthenicand paraffinic hydrocarbon oil, polyglycols and glycols, alkyl esters ofdibasic acids, e.g., dioctyl phthalate, dioctyl sebacate, dioctyladipate, diisodecyl glutarate, dioctyl azolate, alkyl sulfides, fattyacid esters, e.g., butyl oleate, butyl stearate, octyl epoxy tallate,trioctyl trimellitate, polyester plasticizers, e.g., polymericdi(butoxy-ethoxy-ethyl) adipate, polymers of bis(ethyleneoxy)methanewith disulfide linkages; petroleum sulfonates, alkyl trimellitates; andpolymeric esters.

[0030] The suitable finely divided carrier materials include carbonblack, metal oxides, such as aluminum oxide, alumina, silica, mineralfillers, such as clay, talc and betonite, aluminosilicate, zeolites,calcium silicate and similar carriers. Preferred carriers have a surfacearea of from about 75 to about 300 m²/gm. A particularly preferredcarrier is amorphous silica available from Pittsburgh Plate GlassCompany under the tradename HISIL®0233 and HISIL® ABS.

[0031] The amount of the additive effective to cure the chlorinatedpolymer will vary as a function of the halogen content in thehalogenated polymer. Generally, the additives are employed in the rangefrom about 0.1 to about 10.0 parts by weight per 100 parts by weight ofhalogenated polymer present in the curable composition. More preferably,the additives of the present invention are present in the amount fromabout 0.5 to about 5.0 parts by weight per 100 parts by weight of thehalogenated polymer. If a diluent or a carrier material is added to thecurable polymer composition, higher levels of the additive may berequired.

[0032] Additional accelerators of the aliphatic or aromatic amine typecan also be used if the halogenated polymer employed for production ofvulcanized rubber is relatively unreactive. The suitable accelerators,among others, include the reaction product of butyraldehyde and aniline(available commercially under the tradename VANAX® RTM 808 from R. T.Vanderbilt Company, Inc.), fatty amines, sulfonamides such asN-cyclohexyl-2-benzothiazolesulfenamide (available commercially underthe tradename DURAX® from R. T. Vanderbilt Company, Inc.) and quaternaryammonium salts, such as tetrabutylammonium bromide andtetraethylammonium chloride. A listing of additional accelerators to beutilized in accordance with the present invention is set forth in“Rubber Chemicals,” J. Van Alphen, pages 1-46 (1973), which isincorporated herein by reference.

[0033] For curing blends of halogenated and non-halogenated polymers,sulfur or other well known sulfur-containing curatives for unsaturatedelastomers may be included in the composition. Examples of suchcompounds include, but are not limited to, sulfur, benzothiazyldisulfide, N-oxydiethylene benzothiazole-2-sulfonamide,2-mercaptobenzo-thiazole, alkyl phenol disulfides, tetraalkylthiuramdisulfide and monosulfide having normal or branched chain alkyl groups,m-phenylene-bismaleimide and N,N′-diarylguanidines.

[0034] Other additives, which may be desirable to effect crosslinkingalong with the derivatives of the present invention, include basic metaloxides, metal hydroxides and metal salts of carboxylic acids. Thetypical additives include zinc oxide, magnesium oxide, zinc stearate andsodium acetate. The magnesium oxide may be synthetic or a naturalmagnesite mineral. The magnesite may be calcined or treated by othersimilar processes to yield a predominantly magnesium oxide product.

[0035] In addition to the curatives, the polymer compositions of theinvention may also include antioxidants, for example, octylateddiphenylamine, diphenyl-p-phenylenediamine and styrenated phenol typeantioxidants. Likewise, the polymer compositions of the invention mayinclude antidegradants, antiozonants, antiflexcracking agents, heatstabilizers and metal poison-inhibitors, which are well known in theart.

[0036] The curable compositions may be prepared and blended using anysuitable mixing device such as a two-roll mill, an internal mixer(Brabender Plasticorder), a Banbury Mixer, a kneader or a similar mixingdevice. The processing and vulcanization techniques are well known inthe art.

[0037] The following non-limiting examples are given to furtherillustrate the additives of the invention and their use in curablepolymer compositions. All percentages and parts are based on weightunless otherwise indicated.

EXAMPLE 1

[0038] (Diisopropyl DTC DMTD)

[0039] 5′-(Diisopropyldithiocarbamyl)-2,5-dimercapto-1,3,4-thiadiazole(i.e., formula (I) where X is hydrogen and R₁ and R₂ are isopropylradicals) was prepared in the following manner. In 100 grams ofisopropyl alcohol 20.5 grams of diisopropylamine was combined with 16grams of carbon disulfide (CS₂) and held at a temperature of about 27°C. for about 1 hour to yield a diisopropyl dithiocarbamic acidintermediate. Subsequently, 30 g of a 2,5-dimercapto-1,3,4-thiadiazolewas added to the mixture along of 20 g of 35 wt. % hydrogen peroxide.The mixture was reacted for about 1 hour at a temperature of about 28°C. to yield the solid end product5′-(diisopropyldithiocarbamyl)-2,5-dimercapto-1,3,4-thiadiazole. Theisopropyl alcohol was filtered off and saved for recovery.

EXAMPLE 2

[0040] (Di-n-butyl DTC DMTD)

[0041] 5′-(Dibutyldithiocarbamyl)-2,5-dimercapto-1,3,4-thiadiazole(i.e., formula (I) where X is hydrogen and R₁ and R₂ are n-butylradicals) was prepared in the following manner. In 100 grams ofisopropyl alcohol 26 grams of dibutyl amine was combined with 16 gramsof CS₂ and held at a temperature of about 40° C. for about 1 hour toyield a dibutyl dithiocarbamic acid intermediate. Subsequently, 30 gramsof 2,5-dimercapto-1,3,4-thiadiazole was added to the mixture along with20 grams of 35 wt. % hydrogen peroxide. The mixture was reacted forabout 1 hour at a temperature of about 28° C. to yield the liquid endproduct 5′-(dibutyldithiocarbamyl)-2,5-dimercapto-1,3,4-thiadiazole.

EXAMPLE 3

[0042] (Piperidyl DTC DMTD)

[0043] 5′-(Piperidyldithiocarbamyl)-2,5-dimercapto-1,3,4-thiadiazole(i.e., formula (I) where X is hydrogen and R₁ and R₂ form a six-memberedring) was prepared in the following manner. In 100 grams of isopropylalcohol 17 grams of piperidine was combined with 16 grams of CS₂ andheld at a temperature of about 35° C. for about 1 hour to yield apiperidyl ditluocarbamic acid intermediate. Subsequently, 30 grams of2,5-dimercapto-1,3,4-thiadiazole was added to the mixture along with 20grams of 35 wt. % hydrogen peroxide. The mixture was reacted for about 1hour at a temperature of about 35° C. to yield the solid end product5′-(piperidyldithiocarbamyl)-2,5-dimercapto-1,3,4-thiadiazole. Theisopropyl alcohol was filtered off and saved for recovery.

EXAMPLE 4

[0044] (Diethyl DTC DMTD)

[0045] 5′-(Diethyldithiocarbamyl)-2,5-dimercapto-1,3,4-thiadiazole(i.e., formula (I) where X is hydrogen and R₁ and R₂ are ethyl radicals)was prepared in the following manner. In 100 grams of isopropyl alcohol20.5 grams of diethylamine was combined with 16 grams of carbondisulfide (CS₂) and held at a temperature of about 27° C. for about 1hour to yield a diethyl dithiocarbamic acid intermediate. Subsequently,30 g of a 2,5-dimercapto-1,3,4-thiadiazole was added to the mixturealong of 20 g of 35 wt. % hydrogen peroxide. The mixture was reacted forabout 1 hour at a temperature of about 28° C. to yield the solid endproduct 5′-(diethyldithiocarbamyl)-2,5-dimercapto-1,3,4-thiadiazole. Theisopropyl alcohol was filtered off and saved for recovery.

EXAMPLE 5

[0046] Vulcanizates incorporating the derivatives of Example 1-4 wereprepared and evaluated. Samples were prepared by compoundingchloropolyethylene polymer with the derivatives of Example 1-4 (neat)and various other additives as listed in Table 1 below. TABLE 1 Sample 12 3 4 5 6 7 Components (parts by weight) Chloropolyethylene⁽¹⁾ 100 100100 100 100 100 100 Carbon Black⁽²⁾ 50 50 50 50 50 50 50 MagnesiumOxide⁽³⁾ 5 5 5 5 5 5 5 Process oil⁽⁴⁾ 30 30 30 30 30 30 30 AmineActivator⁽⁵⁾ 0.8 0.8 0.8 0.8 0.8 — — Retarding Agent⁽⁶⁾ 0.5 InventiveCurative Diisopropyl DTC 2.5 2.5 DMTD Di-n-butyl DTC 2.5 2.5 DMTDPiperidyl DTC DMTD 2.5 Diethyl DTC DMTD 2.5 2.5 Total Parts: 188.3 188.3188.3 188.3 188.8 187.8 187.8

[0047] The compositions were pressed cured at 171° C. for 30 minutes.The samples were evaluated for Torque and Scorch time by ASTM D2084. TheTorque and Scorch results for the samples are listed in Table 2 below.TABLE 2 Oscillating Disk Rheometer - Sample 60 minutes @ 171° C. 1 2 3 45 6 7 Minimum Torque 2.6 2.9 2.0 0.6 2.9 3.2 3.5 (ML) (inch-pounds)Maximum Torque 46.4 49.2 43.9 53.9 45.6 44.3 49.4 (MH) (inch-pounds)Scorch time, (ts2) 1.0 1.4 2.9 1.7 1.6 1.2 1.3 (minutes) Cure time,(tc90) 15.5 11.5 27.5 22.5 10.5 19.0 24.0 (minutes)

EXAMPLE 6

[0048] A comparative study was conducted to evaluate bin-storagestability of vulcanizable composition compounded with di-n-butyl DTCDMTD produced in accordance with Example 2 and the curative “Echo A”which is commercially available from Hercules, Inc. Echo A, CAS. No.51988-14-8, is known in the art as 2,5-dimercapto-1,3,4-thiadiazolemonobenzoate ester which corresponds to the structure:

[0049] Samples were prepared by compounding the components listed inTable 3. Differing amounts of Echo A and di-n-butyl DTC DMTD wereutilized to provide an equimolar ratio of thiadiazole moiety due todiffering molecular weights of the curatives. Likewise, differingamounts of the accelerators Vanax® 808 Liquid and Durax® were alsoutilized provide an equimolar ratio of accelerator. TABLE 3 ComponentsSamples (parts by weight) 8 9 10 11 12 Tyrin ® CPE0136 100 100 100 100100 N650⁽¹⁾ 40 40 40 40 40 Atomite ® Whiting⁽²⁾ 75 75 75 75 75 Dioctylphthalate (DOP) 15 15 15 15 15 Sundex ® 790 20 20 20 20 20 Elastomag ®170⁽³⁾ 7.5 10 5 5 10 Carbowax ® 3350⁽⁴⁾ 1 1 1 1 1 PE617A⁽⁵⁾ 2 2 2 2 2Di-n-butyl DTC DMTD — 5.02 5.02 5.02 5.02 Echo A 2.5 — — — — Vanax ® 808Liquid⁽⁶⁾ 0.8 — — — — Durax ®⁽⁷⁾ — 1.5 1.5 0.5 0.5 Total Parts: 263.8269.5 264.5 263.5 268.5

[0050] Samples were evaluated for Mooney Parameters using a small rotor(MS), Torque and Scorch times, and Physical properties, with the resultsbeing listed Table 4. TABLE 4 Sample 8 9 10 11 12 Mooney Scorch, MS @121° C. Initial Viscosity (MU) 42.34 41.97 42.13 42.94 43.37 MinimumViscosity (MU) 29.8 29.12 28.93 31.15 31.25 Final Viscosity (MU) 44.8244.15 43.94 46.17 46.27 Mooney Scorch, MS @ 121° C. Aged 14 days at 40°C./95% relative humidity Initial Viscosity (MU) 145.32 69.45 79.18 89.4276.9 Minimum Viscosity (MU) 70.78 38.35 43.99 54.65 46.84 FinalViscosity (MU) 86.07 48.24 56.69 62.91 52.8 Change Initial Viscosity(MU) 102.98 27.48 37.05 46.48 33.53 Change Minimum Viscosity (MU) 40.989.23 15.06 23.5 15.59 Oscillating Disk Rheometer - 60 minutes @ 160° C.Minimum Torque (ML) (dNm) 2.02 1.98 2.14 1.98 2.06 Maximum Torque (MH)(dNm) 20.28 19.13 22.79 19.43 17.49 Scorch time (ts2) (minutes) 1.821.85 1.45 1.27 1.64 Cure time (tc90) (minutes) 6.6 27.96 27.42 24.0825.84 Physical Properties @ RT - Cure t95 + 5.0 Minutes - 160° C.Hardness - Shore A 76 72 73 72 74 Tensile Break (MPa) 11.25 12.15 12.5212.87 11.52 Elongation Break (%) 341.9 407.8 405.4 418.8 435.9 200%Modulus (MPa) 7.4 7.03 6.93 6.77 6.47

[0051] Apparent from Table 4, samples incorporating the derivatives ofthe invention as a curative exhibited significantly improved stabilityover the sample containing Echo A, which is considered the standardcurative for halogenated polymers. For example, the comparative samplecontaining Echo A (sample 8) exhibited an increase in initial viscosityof 102.98 Mooney units (MU) after being stored for 14 days. To thecontrary, the inventive samples (samples 9-12) exhibited increases ininitial viscosity of only 27.48, 37.05, 46.48 and 33.53, respectively.Similar improvements in the change of minimum viscosity were alsoexhibited.

EXAMPLE 7

[0052] (S,S′-DMTD-bis(Piperazinyl DTC Disulfide))

[0053]S,S′-(2-thio-5-mercapto-1,3,4-thiadiazole)-bis(1,4-piperazine-dithiocarbamatedisulfide) (i.e., formula (III) where X is hydrogen) was prepared in thefollowing manner. 17.2 grams of piperazine was combined with 30.4 gramsof CS₂ in a solvent mixture of 70 grams water and 150 grams of isopropylalcohol. The mixture was held for about 1 hour at 30° C. to yield abis(1,4-piperazinedithiocarbamic acid) intermediate. Subsequently, 60grams of 2,5-dimercapto-1,3,4-thiadiazole was added to the mixture alongwith 38.9 grams of 35 wt. % hydrogen peroxide. The mixture was reactedfor about 3 hours at 42° C. to yield the solid end productS,S′-(2-thio-5-mercapto-1,3,4-thiadiazole)-bis(1,4-piperazine-dithiocarbamatedisulfide).

EXAMPLE 8

[0054] A study was conducted to evaluate S,S′-DMTD-bis(Piperazinyl DTCDisulfide) prepared in accordance with Example 7 with the di-n-butyl DTCDMTD prepared in accordance with Example 2. The samples were prepared bycompounding the components listed in Table 5. TABLE 5 Sample Components(parts by weight) 13 14 Tyrin ® CMO136 100 100 N774 50 50 Maglite ® D 55 Sundex ® 790 30 30 Durax ® 1 1 S,S′-DMTD-bis(Piperazinyl DTC 2.5Disulfide) Di-n-butyl DTC DMTD 5.0*

[0055] The compositions were pressed cured at 171° C. for 30 minutes.The samples were evaluated for Torque and scorch time by ASTM D2084 andMooney parameters by ASTM D1646 using a small rotor (MS). The resultsare listed in Table 6 below. TABLE 6 Sample 13 14 Mooney Scorch, MS @121° C. Minimum Viscosity, t5 (minutes) 39.9 40.6 Scorch, t5 (minutes)28.0 8.0 Oscillating Disk Rheometer @ 171° C. Minimum Torque(inch-pounds) 0.7 0.7 Maximum Torque (inch-pounds) 10.7 10.5 Scorch time(ts2) 8.7 1.6 Cure time (tc90) (minutes) 41.6 26.3

EXAMPLE 9

[0056] The combined effectiveness of S,S′-DMTD-bis(Piperazinyl DTCDisulfide) prepared in accordance with Example 7 with the di-n-butyl DTCDMTD prepared in accordance with Example 2 was evaluated. The sample wasprepared by compounding the components listed in Table 7. TABLE 7Components Sample (parts by weight) 15 Tyrin ® CMO136 100 N774 50Maglite ® D 5 Sundex ® 790 30 Durax ® 1 S,S′-DMTD- 2.5 bis(PiperazinylDTC Disulfide) Di-n-butyl DTC DMTD 1.25

[0057] A portion of the unaged sample was vulcanized, while anotherportion was aged for 7 days at 37.8° C. at 100% relative humidity(RH).The vulcanizates were formed by press curing for 30 minutes at 171° C.Mooney parameters, Scorch time and Torque were evaluated as in Example8. The results are listed in Table 8. TABLE 8 Sample 15-Unaged 15-AgedMooney Scorch, MS @ 121° C. Minimum Viscosity, t5 (minutes) 40.2 46.7Scorch, t5 (minutes) 14.5 16.7 Oscillating Disk Rheometer @ 171° C.Minimum Torque (inch-pounds) 0.7 0.9 Maximum Torque (inch-pounds) 15.414.6 Scorch time (ts2) 2.9 3.5 Cure time (tc90) (minutes) 22.9 28.3

[0058] Although the invention has been illustrated by reference tospecific embodiments, it will be apparent to those skilled in the artthat various changes and modifications may be made which clearly fallwithin the scope of the invention, and are intended to be claimed.

We claim:
 1. An additive comprising a dithiocarbamyl-1,3,4,-thiadiazolederivative having formula (I), or an isomer thereof:

where R₁ and R₂ are independently a radical being either an alkyl, acycloalkyl, an alkenyl, an aryl, an arylalkyl, or an alkylaryl, or R₁and R₂ together form a 3- to 7-membered cyclic ring structure; and X is(i) hydrogen, (ii) a dithiocarbamyl radical having formula (II):

where R₃ and R₄ are independently a radical being either an alkyl, acycloalkyl, an alkenyl, an aryl, an arylalkyl, or an alkylaryl, or R₃and R₄ together form 3- to 7-membered cyclic ring structure, or (iii) amixture thereof.
 2. The additive of claim 1, wherein X is hydrogen, andR₁ and R₂ are each ethyl.
 3. The additive of claim 1, wherein X ishydrogen, and R₁ and R₂ are each isopropyl.
 4. The additive of claim 1,wherein X is hydrogen, and R₁ and R₂ are each selected from the groupconsisting of butyl, isobutyl and mixtures thereof.
 5. The additive ofclaim 1, wherein X is hydrogen, and R₁ and R₂ together form a 6-memberedcyclic ring structure.
 6. The derivative of claim 5, wherein the6-membered cyclic ring structure is a piperidyl radical.
 7. The additiveof claim 1, further comprising a diluent.
 8. A curable polymercomposition comprising a major amount of at least one halogenatedpolymer and at least one additive comprising adithiocarbamyl-1,3,4,-thiadiazole derivative having formula (I), or anisomer thereof:

where R₁ and R₂ are independently a radical being either an alkyl, acycloalkyl, an alkenyl, an aryl, an arylalkyl, or an alkylaryl, or R₁and R₂ together form a 3- to 7-membered cyclic ring structure; and X is(i) hydrogen, (ii) a dithiocarbamyl radical having formula (II):

where R₃ and R₄ are independently a radical being either an alkyl, acycloalkyl, an alkenyl, an aryl, an arylalkyl, or an alkylaryl, or R₃and R₄ together form 3- to 7-membered cyclic ring structure, or (iii) amixture thereof.
 9. The curable polymer composition of claim 8, whereinX is hydrogen, and R₁ and R₂ are each ethyl.
 10. The curable polymercomposition of claim 8, wherein X is hydrogen, and R₁ and R₂ are eachisopropyl.
 11. The curable polymer composition of claim 8, wherein X ishydrogen, and R₁ and R₂ are each selected from the group consisting ofbutyl, isobutyl and mixtures thereof.
 12. The curable polymercomposition of claim 8, wherein X is hydrogen, and R₁ and R₂ togetherform a 6-membered cyclic ring structure.
 13. The curable polymercomposition of claim 8, wherein the halogenated polymer is a chlorinatedpolymer.
 14. The curable polymer composition of claim 13, wherein thechlorinated polymer is selected from the group consisting ofhomopolymers of epichlorohydrin, copolymers of epichlorohydrin andethylene oxide or propylene oxide, polychloroprene, chlorinatedpolyolefins, chlorosulfonated polyolefin, polychloroalkylacrylates,chlorobutyl rubber and mixtures thereof.
 15. The curable polymercomposition of claim 13, wherein the chlorinated polyolefins ischloropolyethylene.
 16. An additive comprising adithiocarbamyl-bis-1,3,4,-thiadiazole derivative having formula (III),or an isomer thereof:

where X is (i) hydrogen, (ii) a dithiocarbamyl radical having formula(II):

where R₃ and R₄ are independently a radical being either an alkyl, acycloalkyl, an alkenyl, an aryl, an arylalkyl, or an alkylaryl, or R₃and R₄ together form 3- to 7-membered cyclic ring structure, or (iii) amixture thereof.
 17. The additive of claim 16, wherein X is hydrogen.18. The additive of claim 16, further comprising a diluent.
 19. Acurable polymer composition comprising a major amount of at least onehalogenated polymer and at least one additive comprising adithiocarbamyl-bis-1,3,4,-thiadiazole derivative having formula (III),or an isomer thereof:

where X is (i) hydrogen, (ii) a dithiocarbamyl radical having formula(II):

where R₃ and R₄ are independently a radical being either an alkyl, acycloalkyl, an alkenyl, an aryl, an arylalkyl, or an alkylaryl, or R₃and R₄ together form 3- to 7-membered cyclic ring structure, or (iii) amixture thereof.
 20. The curable polymer composition of claim 19,wherein X is hydrogen.
 21. The curable polymer composition of claim 19,wherein the halogenated polymer is a chlorinated polymer.
 22. Thecurable polymer composition of claim 21, wherein the chlorinated polymeris selected from the group consisting of homopolymers ofepichlorohydrin, copolymers of epichlorohydrin and ethylene oxide orpropylene oxide, polychloroprene, chlorinated polyolefins,chlorosulfonated polyolefin, polychloroalkylacrylates, chlorobutylrubber and mixtures thereof.
 23. A method of preparing a cured polymercomposition, which comprises: admixing at least one halogenated polymerwith at least one additive including at least one thiadiazole derivativeselected from the group consisting of: (a) adithiocarbamyl-1,3,4,-thiadiazole derivative having formula (I), or anisomer thereof:

where R₁ and R₂ are independently a radical being either an alkyl, acycloalkyl, an alkenyl, an aryl, an arylalkyl, or an alkylaryl, or R₁and R₂ together form a 3- to 7-membered cyclic ring structure; and X is(i) hydrogen, (ii) a dithiocarbamyl radical having formula (II):

where R₃ and R₄ are independently a radical being either an alkyl, acycloalkyl, an alkenyl, an aryl, an arylalkyl, or an alkylaryl, or R₃and R₄ together form 3- to 7-membered cyclic ring structure, or (iii) amixture thereof; (b) a dithiocarbamyl-bis-1,3,4,-thiadiazole derivativehaving formula (III), or an isomer thereof:

where X is (i) hydrogen, (ii) a dithiocarbamyl radical having formula(II):

where R₃ and R₄ are independently a radical being either an alkyl, acycloalkyl, an alkenyl, an aryl, an arylalkyl, or an alkylaryl, or R₃and R₄ together form 3- to 7-membered cyclic ring structure, or (iii) amixture thereof; and curing the admixture to form the cured composition.24. The method of claim 23, wherein at least one thiadiazole derivativeis a derivative having formula (I), X is hydrogen, and R₁ and R₂ areeach ethyl.
 25. The method of claim 23, wherein at least one thiadiazolederivative is a derivative having formula (I), X is hydrogen, and R₁ andR₂ are each isopropyl.
 26. The method of claim 23, wherein at least onethiadiazole derivative is the derivative having formula (I), X ishydrogen, and R₁ and R₂ are selected from the group consisting of butyl,isobutyl and mixtures thereof.
 27. The method of claim 23, wherein atleast one thiadiazole derivative is the derivative having formula (I), Xis hydrogen, and R₁ and R₂ together form a 6-membered cyclic ringstructure.
 28. The method of claim 23, wherein at least one thiadiazolederivative is the derivative having formula (III) and X is hydrogen. 29.The method of claim 23, wherein the halogenated polymer is a chlorinatedpolymer.
 30. The method of claim 29, wherein the chlorinated polymer isselected from the group consisting of homopolymers of epichlorohydrin,copolymers of epichlorohydrin and ethylene oxide or propylene oxide,polychloroprene, chlorinated polyolefins, chlorosulfonated polyolefin,polychloroalkylacrylates, chlorobutyl rubber and mixtures thereof. 31.The curable polymer composition of claim 29, wherein the chlorinatedpolyolefins is chloropolyethylene.